<rdar://problem/5614257> Crash in timer / hashtable code due to uncaught...

    <rdar://problem/5614257> Crash in timer / hashtable code due to uncaught exception

        Don't use callback-based timers, since these cause Windows to eat Windows crashes
        in code the timers call.

        Windows appears to be defending against "shatter" attacks partially by setting
        up a structured exception block while dispatching callback-based WM_TIMERs.

        I verified this by adding a divide by zero into some timer callback code.
        In the case where the timer was dispatched via a callback, the divide by zero
        exception was silently handled and ignored, with execution continuing after
        our call to DispatchMessage.  When processed via the WNDPROC, no SEH
        block was established by Windows, and our divide by zero generated a real
        crash (which is what we wanted).

        Windows handling our crashes for us led us to leave the timer data structures
        in an invalid state so the next time a timer was set, we'd crash accessing an
        invalid HashMap of timer data.

        Reviewed by Hyatt.

        * platform/win/SharedTimerWin.cpp:
        (WebCore::TimerWindowWndProc):
        (WebCore::setSharedTimerFireTime):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@28500 268f45cc-cd09-0410-ab3c-d52691b4dbfc